In recent years, along with the popularization of hybrid vehicles, electric vehicles, and others, there are growing demands for lithium ion secondary batteries to be used in drive power sources thereof. Accordingly, needs for high output power are increasing. To realize the high output power of a lithium ion secondary battery, it is necessary to reduce energy loss during large current emission. Thus, the technique of reducing the internal resistance of an electrode sheet has recently received attention.
As the technique of reducing the internal resistance of an electrode sheet, for example, Patent document 1 discloses an invention related to a lithium ion secondary battery in which an adhesive layer is formed on at least one surface of a current collecting foil, and a charged electrode material (complex particles containing electrode active material) is supplied onto the adhesive layer to form an electrode layer.